The present invention relates to cooking and, more particularly, to smart cooking appliances.
Inductive cooking surfaces are becoming more popular with consumers as they become more affordable. They are safer in some regards because they do not rely on a flame or other direct heat and typically have better overall performance, including faster heating time.
Most inductive cooking surfaces operate by running AC power through an inductive element in order to generate a magnetic field. When a metal cooking appliance, such as a pan, is placed in the field, eddy currents are generated on the pan. The energy from the eddy currents is dissipated as heat, causing the pan—and, by conduction, its contents—to be heated.
Most conventional cooking surfaces include controls to adjust the amount of heat. For example, many ovens, ranges, microwaves and toasters include knobs or keypads that enable a user to manually set the heat applied (e.g., the temperature of the oven) and the cooking time. With electric stoves the control varies the power delivered to an electric heating element. With a gas stove the control varies the flame size. In both cases, the temperature of the pan is not measured directly.
In some inductive cooking surfaces, the temperature of the cooking appliance is controlled by a microprocessor that adjusts the current level to correspond to a chosen heating level. A current measurement of the AC power being applied to the inductive cooking surface provides indirect feedback indicative of the amount of dissipated power, and therefore heat being produced in the pan. The lack of direct temperature control feedback can make it difficult to predict pan temperatures with the desired level of accuracy.
One attempt to enhance the control of an inductive cooking surface is to use a thermo-couple touch-pad. The thermo-couple touch-pad is attached to the inductive cooking surface and contacts the bottom of the pan when the pan is placed on the cooking surface in order to provide direct temperature feedback to the inductive cooking surface microprocessor during operation. This type of feedback is typically used to shut down the induction cooking surface in the event of overheating. Physical contact between the thermo-couple touch pad and the bottom of the pan can be problematic because of misalignment and malfunction issues.
Some inductive cooking surfaces have addressed these issues by providing wireless power to heating electronics housed on the cooking appliance itself instead of heating by directly exciting the bottom of a metallic pan. That is, the cooking appliance may apply the received wireless power to an internal electric heating element. In this configuration, because an electric heating element is used, many of the drawbacks associated with electric stoves persist. One embodiment of an inductive cooking surface that includes this approach is described in U.S. Pat. No. 7,355,150, which is herein incorporated by reference in its entirety.